As will be apparent from the aforementioned copending application, a plain bearing is a bearing which has no active element of the roller type, but rather is a member which is interposed between two relatively displaceable elements to contribute a certain friction characteristic to the relative movement thereof.
The most typical use of a plain bearing is a sleeve between two relatively rotating members, the sleeve being affixed to one of these members and having a surface with predetermined friction characteristics engaging the other of these relatively rotatable elements, i.e. a sliding-contact surface.
For instance, the sleeve can be mounted on a shaft and can be rotatably entrained therewith in a bearing housing, in which case the friction surface runs slidingly over a counter surface of this housing. Alternatively, the sleeve may be stationarily fitted in the housing and will have its friction surface slidably engaging the shaft. Other plain bearings can be utilized as thrust bearings, i.e. bearings in which the friction surface lies transversely to the axis of rotation, and even as combined thrust and radial bearings wherein the friction surface can be inclined both to a radius and to the axis of rotation, e.g. can be a conical surface.
The characteristics which such a plain bearing must have will also be apparent from the aforementioned application and one need only point out that normally the friction surface should be distinguished by its long wear, possibly a self-lubricating characteristic, its ability to withstand pressure and heat, its low coefficient of sliding friction and like characteristics. In some cases, less than a maximum antifriction property may be desirable and hence we refer to a predetermined or given friction characteristic of the surface hereof.
In that application, a fiber-reinforced synthetic resin sliding-contact layer is described in which the fiber reinforcement phase consists of short carbon fibers while the matrix is a thermoplastic synthetic resin or a mixture of two or more thermoplastic synthetic resins from the group of polyarylether, polyarylketones, polyarylsulfides, polyarylsulfones and polyaryloxides. To the roughened surface of the metallic carrier or substrate, the reinforcement layer which can include additives for improving or modifying the sliding or friction characteristics are applied, the additives generally being solid lubricant particles with a particle size which is less than or equal to 40 microns.
The composite structure which thus results has been found to be highly effective in providing a firm bond of the sliding-contact layer at the carrier layer, good bonding of the short fibers in the synthetic resin matrix, and many of the advantageous characteristics outlined above.
However, increased temperature resistance, a greater reinforcing effect of the fiber reinforcement and an increased ability of the sliding-contact layer to accommodate friction-modifying additives are nevertheless desirable.